Lymphoid Flashcards
Differentials for increase in size of lymphoid organs
Thymus - thymoma, thymic lymphoma, thymic branchial cysts, hemorrhage/hematoma
LN- hyperplasia, inflammation, neoplasia (lymphoma or metastatic)
Differentials for nodules in spleen
Hemangiosarcoma
Lymphoma
Nodular hyperplasia
Causes of hypoplasia of lymphoid organs
Severe combined immunodeficiency (SCID)
Atrophy (involution or lympholysis)
Causes of lympholysis
Viruses (distemper, parvo, panleuk)
Corticosteroids
Nutritional (starvation, zinc deficiency, acrodermatitis of bull terriers)
Toxic (polychlorinated biphenyls (PCB))
Why is thymic hypoplasia and lymphoid atrophy important?
Immunological dysfunction
Getting sicker than expected, getting sick more often, difficult diagnosis
Clinical signs associated with increase in size of lymphoid organs
Respiratory tract - dyspnea, cough
Digestive tract - regurgitation
CVC - edema, swollen head and neck
thoracic duct effusion - chylothorax
Cell type and malignancy of thymomas
Cell type- epithelial cells
NOT associated with viral cause
Metastasis and invasion of adjacent structures is NOT common
Paraneoplastic syndromes associated with thymomas
Acquired autoimmune disorders (Myasthenia, polymyositis)
Exfoliative dermatitis (cats)
Difference between thymoma and thymic lymphoma
Thymoma- tumor of epithelial component
Thymic lymphoma - tumor of lymphocytes/blasts (Usually T lymphocytes)
Cell type and malignancy of thymic lymphoma
Cell type- neoplasplastic lymphocytes
Has been associated with young, FeLV+ cats
Tend to be aggressive and invasive
Thymic branchial cysts
Develop from vestiges of fetal branchial arch system
Not neoplastic
Presents like thymoma
Histopathology of LN, where would you see neoplastic cells first?
Subcapsular sinuses
LN hyperplasia
Reactive node/reactive lymphadenopathy
Architecture of node is maintained (fish flesh, tan, homogenous)
Cells are large immature lymphoblasts and small mature lymphocytes +/-increased plasma cells and/or macrophages
Mitotic index may be mildly-moderately increased
Salmon poisoning, FIV
Lymphadenitis
INFLAMMATION
Node is actually involved, not just draining a site
Grossly: swollen, gray-red, engorged, painful
Histo: Inflammatory cells +/- microorganisms
Functions of spleen
Host immune response
Filtration of unwanted elements from blood via phagocytosis
Hematopoeisis
Reserve blood storage
Differentials for single mass on spleen
Leiomyosarcoma
Hemangioma
Hemangiosarcoma
Differentials for diffuse splenomegaly
Lymphoma
Myeloid leukemia
Mast cell tumor (esp cats)
Splenitis
Most common canine lymphoma
Multicentric (80%)
What would you see on histopath of lymphoma biopsy?
Effacement of normal architecture
Is multicentric lymphoma evident in blood?
Not commonly
Pathogenesis of hypercalcemia of malignancy
“Pseudohyperparathyroidism”
Caused by tumor secretion of PTHrP
Patients present with PU/PD due to Ca inhibition of ADH
